A genomic view on lactic metabolism.

Area of Science:

• Microbiology
• Metabolic Engineering
• Genomics

Background:

• Lactic acid bacteria (LAB) have a complex relationship with humans, acting as beneficial probiotics, commensals, and potential pathogens.
• LAB significantly influence food quality and safety, serving as both fermentation agents and spoilage organisms.
• The carbohydrate metabolism of LAB has been extensively studied for over a century due to their multifaceted roles.

Purpose of the Study:

• To integrate existing knowledge of lactic acid metabolism with current genomic data for LAB.
• To elucidate the metabolic strategies differentiating homofermentative and heterofermentative LAB.
• To explore how ecological adaptations shape LAB metabolic preferences.

Main Methods:

• Review of existing literature on LAB carbohydrate metabolism.
• Analysis of genomic information available for various LAB species.
• Comparative analysis of metabolic pathways and ecological niches.

Main Results:

• Homofermentative and heterofermentative LAB exhibit distinct energy generation pathways and substrate utilization, leading to diverse ecological distributions.
• Many LAB possess electron transfer chains enabling the use of various terminal electron acceptors, including oxygen, nitrate, and iron.
• Metabolism of organic acids and diols enhances LAB acid resistance and survival in stationary phases.
• Distinct metabolic traits correlate with specific ecological niches, differentiating insect-associated, vertebrate-host adapted, free-living, and domesticated LAB.

Conclusions:

• Understanding LAB metabolic preferences, linked to phylogeny and ecological adaptation, is crucial for selecting appropriate starter cultures.
• This knowledge supports the development of both traditional and innovative food fermentation processes.
• Genomic insights significantly enhance our comprehension of LAB's metabolic diversity and ecological roles.